Organic semi-permeable membranes provided with a plurality of separate longitudinal passageways have important advantages with respect to conventional hollow fibers. In effect, they have a high mechanical strength which simplifies notably the problems of handling. Moreover, the speeds of production are accelerated due to the fact that a lesser length of membrane is necessary for producing a bundle. Finally, the provision of filtration modules is found to be markedly simplified. Such advantages have led to a development of the use of these membranes in which techniques of production or applications are particularly described in the following patents: DE-A-3,022,313; WO-A-8102750; FR-AL 2,445,163; and JP-A-5982,906. However, the known techniques, and particularly those described in these patents, do not permit the mastery in a rational manner of all of the production parameters for membranes and especially conferring on these membranes particular, predefined structures, and mastery in a precise manner of the external dimensions of these membranes as well as their passageways.
The present invention seeks to fulfill these deficiencies, and has as its principal object to provide a process permitting providing membranes having a particularly well defined structure and of which the dimensions, as well as the dimensions of their passageways, are precisely defined.